low efficiency speaker vs. high efficiency speaker?

I'm sure that Gregm means well, but after reading his response, I have to confess that I would be really confused by now if I didn't understand the subject of speaker efficiency very well.

First of all, the speaker is usually fed the equivalent of a 1 Watt (not 1 volt) test signal at a standard test frequency (usually 1 kHz) and the speaker's output is then measured in decibels (dBs). Secondly, his references to voltage and current are essentially vague, meaningless generalizations -- and an entirely different issue unto itself. Lastly, can anyone tell me what Greg means by his statement that efficient speakers "can take the mikey out of the electronics in no time"? (This one really threw me!) Greg, who is this "mikey" you speak of, and how did he get into the electronics in the first place??

Anyway, as Onhwy61 notes, the speakers efficiency rating has no direct relationship to its sound quality. However, the efficiency of a speaker will dictate how much amplifier power you will need to achieve a given volume level in your listening room. The size of the room itself, its acoustic properties, and distance from the speaker to the listening position, as well as the listener's preferred level of volume all factor into how much amplifier power will be needed.

For every 3 dB you increase the volume you need double the amplifier power in watts. So, if you have a speaker that is providing 93 dB with 1 watt input (dB ratings are usually measured at 1 meter from the speaker), then to go to 96 dB the amp must deliver 2 watts, to get 99 dB the amp must deliver 4 Watts, and 8 Watts for 102 dB, etc. This is without considering room acoustics or the actual distance to the listener. If you are pumping up the bass then this compounds the required amplifier power likewise.

If you are using a speaker that delivers 86 dB output for 1 watt input then doubling the amp power every 3 dB will necessitate more than 40 watts to deliver the same 102 dB level that is attained with only 8 watts from the 93 dB efficient speaker.

So if you'd like to hit 110 dB peaks in a large room with 86 dB efficient speakers then you had better find an amp that can deliver a few hundred watts per speaker.

That's why folks who prefer to use low-power SET tube amps for their unique sonic qualities need speakers that border on 100 dB/watt efficiency. To hit 106 dB peaks with such high efficiency would only require 4 watts.

I hope this helps. :)

bear in mind that most listening happens w/ less than 10w--run the math on an 88db speaker, and you're well into the upper 90s w/ less than 10w. do the same w/ a 93db speaker, and you're more than covered.

however, its FAR more costly to build a quality 200w amp than it is to build a quality 20w amp. all amps are not equal! if the first watt isn't first class top notch, the other 199 only get worse.

as a result, you're often best served (financially and acoustically) if you go hi-sens, lo watt (class A only). it was one of the best decisions i ever made.

Plato, thanks for the corrections & for clarifying what I was trying (unsuccessfully) to convey! As to "mikey": my idea was that a good speaker, be it efficient, will reveal shortcomings in the electronics. So, "make fun" of those electronics... i.e. despite the fact that lower amp output + hi-efficiency will produce the same db level as mega horsepower+lower efficiency, the amp quality remains paramount. Higher efficiency does not make speakers forgiving.

Sorry for the confusion.

Cheers!

Hi,
there are some very interesting answers. Maybe I can give an experience from the musical side. I used Planars, then dynamic speakers and now I use horns. Let's see it from speakers who does it right , no matter of construction.
With low efficient speakers you need some powerful amps to control them in every area. Powerful, when you want to hear every detail even with low volume. When you want full dynamic with low volume, then there is the first problem. Very difficult.
Next : Powerful amps are everywere, good sounding ones are available too, but the combination, powerful AND Good sounding is rare and normally not cheap.

With high efficient speakers there it is much easier to match this one with a good sounding amp. No matter solid State or Tube. Much more amps sound much better when they don't have to deliver all they can give.
There are people out there who believe that the first Watt is the most important, but this is another story.

So, you get much more satisfying listening results with such a combination when you want ( or have to ) listen with low volume.

You hear normally much more microdynamics and an absolutely effortless reproduction of music.
Sometimes when I listen to Radio ( MD 108 ) I am totally amazed when I hear the singer's breathing. Via Radio !
It's on the source.
My speakers have 99 dB and I use them with Pass mono amps ( 100 W per side, normally a total overkill, but it works excellent ).

The feeling of " being there " is with such a speaker really possible.

Some great responses above, and here's another point to consider. Many solid state desingers will not admit it, but quite a few designs sound better in their 1st 20% of power delivered, than in the next 80% left. In many ways this makes perfect electrical sense. One example: There are class A/B amplifiers that actually run in full class A up to a small point of the power amps rating, then "switch over" to full class A/B as they are required to deliver more power. If you had a speaker that was extremely efficient, you would then be having your amplifier run mostly in it's better sounding Class A state i.e., ending up with a better sounding system.